The invention relates to a portable handheld work apparatus including an overhead branch cutter.
German patent publication 3,213,185 discloses a portable handheld work apparatus configured as an overhead branch cutter. The overhead branch cutter is essentially defined by a carrying tube having a first end on which a drive motor is mounted. A work tool is mounted on the second end of the carrying tube. The work tool is an oscillating saw blade which is driven by the drive motor via a shaft in the carrying tube. The work tool extends in the longitudinal direction of the carrying tube. For this reason, during operation, it is not always possible to have the best possible work position of the portable handheld work apparatus as well as the best possible position of the work tool itself.
It is an object of the invention to provide a portable handheld work apparatus which is so configured that the apparatus can be variably adjusted for different work positions.
The portable handheld work apparatus of the invention includes: a carrying tube unit having first and second ends; a drive motor mounted on the first end; a work tool mounted on the second end; a shaft arranged in the carrying tube unit connecting the drive motor to the work tool so as to permit the drive motor to drive the work tool; the carrying tube unit being subdivided at a location between the first and second ends into a first carrying tube section carrying the drive motor and a second carrying tube section carrying the work tool; the first and second carrying tube sections defining first and second longitudinal axes, respectively; a ball-and-socket joint connecting the first and second carrying tube sections to each other at the location so as to permit the first and second carrying tube sections to be rotated and pivoted with respect to the first and second longitudinal axes thereof; and, means for fixing the ball-and-socket joint in an adjusted position corresponding to a wanted orientation of the first and second longitudinal axes relative to each other.
A pivotable and rotatable connection of the carrying tube sections is provided by dividing the carrying tube of the portable handheld work apparatus into these two sections. The two carrying tube sections are adjustable relative to each other by a ball-and-socket joint and means are provided for fixing the ball-and-socket joint in an adjusted position. In this way, a work tool of the portable handheld work apparatus mounted on the carrying tube can be continuously pivoted relative to the longitudinal axis of the carrying tube and can also be rotated and fixed in the adjusted position. With this configuration, it is possible to adjust different positions of the work apparatus on the carrying tube of the portable handheld work apparatus whereby different work positions are possible in dependence upon the particular application of the handheld portable work apparatus. The ball-and-socket joint is essentially formed from a shell-shaped ball, which is hollow in its interior, and a shell-shaped socket which engages around the ball over its periphery. The socket is at least clamped at a circular-shaped location on the ball by a clamping device which is preferably arranged on the socket. It is practical to configure the socket and the ball to have half shell shapes with the openings thereof directed toward each other. The clamping device is preferably formed by a clamp band changeable in its circumferential length. The clamp band is held on the outer side of the socket, namely, at the edge thereof facing toward the ball. Preferably, the clamp band spans the socket about its periphery. The clamp band is guided in a peripheral slot on the edge of the socket and the peripheral slot is preferably of a rectangular shape.
It is practical to manufacture the socket from parts having the same form in order to simplify the manufacture thereof. The form-like parts or half shells can be connected to each other in a suitable manner so as to be force-tight or also form-tight. The half shells of which the socket is formed are preferably threaded. A gap is formed between the half shells in the region of the spherical segment of the socket. This gap is covered from the inner side of the spherical segment by strip-shaped tongues which are formed as one piece on each half shell. The gap makes possible a resilient support of the socket against the ball under the action of the clamping device. A sealing ring, preferably made of elastomeric material, is placed about the ball in the axially overlapping region between the ball and the socket. The sealing ring functions to seal the interior of the ball-and-socket joint and strengthens the friction-tight connection between the ball and socket. The sealing ring is preferably arranged on the edge of the ball in a peripheral slot of the ball. The edge of the ball faces toward the socket. The sealing ring lies with its sealing surface approximately in the outer contour of the ball. In this way, a spherical segment is formed which is almost homogeneous on its outer side.
For connecting the ball and socket to the respective sections of the carrier tube, a first shaft is fixed to the ball at the apex and a second shaft is fixed to the socket on the apex thereof. These shafts are preferably tubularly-shaped cylindrical shafts. It is practical to configure the respective shafts as one piece with the ball and socket. The shaft on the socket preferably engages in a section of the carrying tube; whereas, the shaft on the ball preferably engages over a section of the shaft. For this purpose, the shaft is configured as a sleeve-shaped shaft and has an inner diameter which is so selected that it can be pushed onto the end of the carrying tube with little play. In this way, a combination of different apparatus types is possible and a subsequent assembly on an already produced apparatus can also be advantageously provided. It can be practical to arrange the ball-and-socket at the end of the carrier tube so that the tube-shaped cylindrical shaft of the ball-and-socket joint which faces away from the carrier tube, engages in a flange of the work tool. The cylindrical shaft then forms an end section of the carrier tube.
It is practical to provide the shaft on the ball with a clamping device for changing the rotational angle of the work tool on the carrier tube. For this purpose, the shaft is provided with two mutually opposite-lying longitudinal slots. The longitudinal slots preferably lead from the shaft end over a portion of the length thereof. A clamping screw projects transversely over each of the longitudinal slots. The clamping screws support themselves on the flange at the shaft end.
The pivot angle of the ball-and-socket joint is delimited by the overlapping of the socket over the ball. The sealing rings on the ball and socket define a stop. The overlapment is preferably effected by a cylinder segment on the socket. The edge of the cylinder segment comes to a stop on the ball when the socket is pivoted relative to the ball. The pivot angle between the longitudinal axis of the carrier tube and the longitudinal axis of the shaft of the ball-and-socket joint, which faces away from the carrier tube, is in the range of 0 to xc2x145xc2x0, preferably 0 to xc2x140xc2x0.
The rotational angle of the ball-and-socket joint about the longitudinal axis of the carrying tube lies in the range of 0 to xc2x1360xc2x0 because the ball can be rotated as desired relative to the socket and vice versa and is again fixable with the clamping device. The shaft in the carrying tube can be configured as a bendable shaft. In lieu of a bendable shaft, it can be practical to configure this shaft as a rigid shaft and to rotatably journal the same in the carrying tube. A pivot joint is provided between the shaft sections and is disposed in the ball-and-socket joint of the carrying tube for transmitting the torque from one shaft section to the other. The shaft sections are connected to each other with the aid of the pivot joint and so that they cannot rotate relative to each other. The shaft ends, which face toward each other in the pivot joint, have hubs for this purpose. The hubs are held in the shaft of the socket and of the ball, respectively, with respective bearings. The hubs are preferably held and guided by ball bearings. On one hub, a pivot ball or star is fixed so that it cannot rotate relative thereto. The pivot ball has a star shape when viewed in cross section. On the other hub, a pivot socket is mounted so that it cannot rotate relative to the hub. The pivot socket has a star shape viewed in cross section. The star or pivot ball engages axially in the socket. A ball bearing race is built in radially between the star and the pivot socket so that the ball bearings can act as torque-transmitting elements in the sense of a constant velocity or universal joint.